#include <stdio.h> 
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
int main()
{
   pid_t pid;
 
   pid = fork();
    if(pid < 0){
   printf("%s fork error\n",__FUNCTION__);
  return 1;
 }else if( pid == 0 ){ //child
 printf("child is run, pid is : %d\n",getpid());
 sleep(5);
 exit(1);
 } else{
 int status = 0;
 pid_t ret = 0;
 do
 {
 ret = waitpid(-1, &status, WNOHANG);//非阻塞式等待
 if( ret == 0 ){
 printf("child is running\n");
 }
 sleep(1);
 }while(ret == 0);
 
 if( WIFEXITED(status) && ret == pid ){
 printf("wait child 5s success, child return code is :%d.\n",WEXITSTATUS(status));
 }else{
 printf("wait child failed, return.\n");
 return 1;
 }
 }
 return 0;
} 
